Second wave of bird flu ups pandemic worries

A new type of flu began making people sick in China in 2013. Researchers quickly discovered that the virus was a type of avian influenza, known as H7N9, never before seen in humans. In one year the virus has surged twice, sickening 370 people in China and killing 115 (according to data available as of February 28).

As with seasonal flu, infections tapered off during the summer of 2013 but reappeared with colder weather. The second wave of H7N9 started earlier in the flu season and has sickened more people than the first wave did.

At least for now, H7N9 doesn’t spread easily from person to person. Only four families have multiple sick members that may have passed the virus through close contact. Scientists worry that if the virus infects many people, it may gain the ability to readily jump between humans, creating a pandemic.

Exposure to live poultry is the main infection route, with 82 percent of sick people in the first wave reporting recent contact with

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